PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.Flats Women Shoes Fabric Glitter Fashion Black Work Casual Bee Any OccasionWomen's ANTONIO MELANI Bright Black Leather Slip On Loafers-Size 5 1/2M NR! , THERESIA LADIES BROWN SUEDE LEATHER SHOES MADE IN GERMANY SZ 6 GREAT CONDITION , JOE FRESH NWOB Sz 9 Ballet Flat Black Leather Calf Hair Rounded Toe Tie AccentCircus by Sam Edelman Ali Halogram Ballet Flats, Slip Ons, Metallic, 7.5 US , Women's Leather Loafer Casual Flat Shoes Rubber Sole Shoes 6 Burgundy/WineRed , Gray Suede & Leather B MAKOWSKY Tilly Elasticized Back Edge Flats w/Bow 6.5 M , ELLIOT LUCCA "Cameo" Print Wool Cabernet Round Toe Wool Lined Wm. Sz. 6 Sample , Dr Comfort Merry Jane Leather Buckle Mary Jane Strap Shoe Womens Sz 7 M , Sigerson Morrison Shoes Belle Ballet Flats Black Leather Size 6 AR0497Keen Sneaker Womens Floral Denim Canvas Hiking Outdoors Flat Shoes Sz 6Dexter Comfort Leather Loafers Beige penny loafers Moc Toe Size 8.5 Women Woven , Womens Embroidery Diamond Rivets Causal Leather Ethnic Style Shoes Flat Loafer sNew Women girls Sneakers Sports Athletic Leisure Running Flat Trainers Shoes , Opportunity Shoes - Corso Como Women's Ramona Ballet Flat Black Size 8.0 wZ2WNike Musique Womens White Leather Dance Shoe Size 9 , Adidas Women's Neo Lite Cloudfoam Racer Slip On Shoes - Grey sz 10 NIB!Mizuno Crusader Womens Running Shoes Fitness Gym Workout TrainersSaucony Womens - Gray Running Shoes Size 9 (362276)Grasshoppers Women's Garnet Peep Toe Fashion Sneaker, Stone/White, Size 6.5 tyKp , Pearl Izumi Womens Running Shoes Size 10 (3851) , Women's Franco Sarto new women’s flats Utmost In Convenience FlatsMerrell Women's 1SIX8 MJ AC Athletic Mary Jane Sneaker J45706 Wmn Sz9M US Eur 40 , Vans Karl Lagerfeld Slip Ons Size 6 Womens !!! , NIKE FREE TR FOCUS FLYKNIT Women's Running shoes NEW MSRP $130 844817 302 GreenNew The North Face: Greenwater Ladies Sport Shoes Sz 10 US,41 EUR,27 cm , Skechers SRR Resistance Shape Ups Toning Walking Shoes Women's US 10NIKE Womens Kawa Slide 834588-401 CHLORINE BLUE/WHITE-OBSIDIAN Womens Size 5 , Adidas Womens Size 7.5 Stellasport Rainbow Training Runner Blue Shoes SneakersCONVERSE All-Star Low Top Sneakers Chuck Taylor Brocade Cream White Women Sz 10 ,
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."